Here’s a fascinating piece of history that escaped much of the world’s notice, when it happened back in 1988.

That’s the year that international pressure finally caused the military dictatorship of Augusto Pinochet to hold an election in Chile, the country he and his fellow generals took over in a bloody coup in 1973. They offered Chileans the chance to endorse the current regime or reject it. Vote “Si” if “stability” and “order,” at the cost of political executions, “disappearances” and one party rule works for you. Vote “No” is you’d rather take a chance on that great unknown – “democracy.”

“No” is about how that “No” campaign was concocted.

Gael Garcia Bernal (“The Motorcycle Diaries”) gives a poker-faced performance as Rene, an ‘80s hip advertising executive who was educated abroad and builds every ad campaign around pop music, “Chile is ready for the future” and mimes. The son of a politician, and a single dad whose estranged wife (Antonia Zegers) is a radical Rene is constantly having to rescue from jail, he comes off as apolitical.

When he’s approached by “an old family friend,” a socialist leader, to take on the ad campaign for “No,” Rene has plenty of reasons to say “No” himself. “The election’s fixed,” insiders complain. They only have 27 days to come up with 15 minute blocks of infomercials to convince voters to side with them. His ad agency boss (Alfredo Castro, menacing, cynical) is against it. Rene’s radical wife is contemptuous of the effort, which will just “legitimize” a murderous regime.

And Rene has all this work – commercials for soap operas, microwave ovens – employing actors, dancers, singers and mimes. He has no time.

But Rene changes his mind. Maybe he likes a challenge. Maybe he wants to convince the wife to come back to him. Maybe he sees this as his legacy, or a great way to boost his career. If he can pull this off, he argues with his boss, “We’ll be famous.”

The voices of leftist dissent are bitter, wounded, grieving for murdered friends and relatives, determined to wipe the regime’s ugly history in its face with their 15 minutes of air time. No, Rene says (in Spanish, with English subtitles).”This doesn’t sell.”

In debates with politicians, colleagues and the passionate director (Nestor Cantillana) who considers Rene a lightweight, Rene argues that” Happiness” is how you reach frightened voters lost in their “hopelessness.” Give me a jingle, he says. Let’s use humor and optimism.

Pablo Larrain’s film matches its “modern” footage with the faded colors and grainy images of TV in the pre-HD era. Archival news footage reminds us of the brutality of the police state and the reasons the government was worried. Pinochet, a shrill martinet when he opened his mouth, wasn’t an easy sell.

“No”, based on a play, gets bogged down in brainstorming sessions, arguments over what props to use on the sets of the commercials and the input of “focus groups.”

But the paranoia plays beautifully, juxtaposing the guarded optimism of the artistic community (most of whom were in the “No” camp) with the stakes – police intimidation, vandalism, arrests.

And the ads themselves, “Coca Cola commercials” the politicians complain, are a retro riot – companeros singing and dancing “No mas” in front of a rainbow flag. With the occasional mime.

They’re just the sort of thing that taught “the world to sing” in the ‘70s and ‘80s. But as silly as they were, in Chile, they made history.

MPAA Rating: R for language

Cast: Gael Garcia Bernal, Antonia Zegers, Alfredo Castro

Credits: Directed by Pablo Larrain, scripted by Pedro Peirano, based on the play by Antonio Skarmeta . A Sony Classics release.